Etching method and process for producing a semiconductor element using said etching method

ABSTRACT

A method for etching an object having a portion to be etched on the surface thereof, comprising a step of immersing said object in an electrolyte solution such that said object serves as a negative electrode; a step of arranging a counter electrode having a pattern corresponding to a desired etching pattern to be formed at said portion to be etched of said object in said electrolyte solution so as to maintain a predetermined interval between said counter electrode and said object, and a step of applying a direct current or a pulse current between said object and said counter electrode to etch said portion to be etched of said object into a pattern corresponding to said pattern of said counter electrode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved etching method, a processfor producing a semiconductor element using said etching method, and anetching apparatus suitable for practicing said etching method. Moreparticularly, the present invention relates to an improved etchingmethod which is simple and excels in selective etching precision andwhich enables to etching an object to be etched into a desirable statewith no or very slight damage at the non-etched region or layer thereof.The present invention also relates to a process for producing asemiconductor element based on said etching method, which comprises asmall number of steps and enables efficient production of semiconductorelement by way of a fast etching, treatment, at a reduced productioncost. By this method a transparent and electrically conductive film of aphotovoltaic element as the semiconductor element can be patterned in adesirable state while repairing defects, such as short circuit defectsof the photovoltaic element. The present invention further relates to anetching apparatus suitable for practicing the above method and process.

2. Related Background Art

In recent years, etching techniques have been widely used during theproduction of various semiconductor elements used in photovoltaicelements including solar cell elements, photodiodes, and the like. Forinstance, in the production of photodiodes and ICs (integratedcircuits), the etching technique has been used in patterning or removingan electrode comprising a metal electrically conductive film ortransparent and electrically conductive film, a base member or asemiconductor layer. Further, in the production of semiconductorelements such as solar cell elements, the etching technique has beenused in patterning or removing an electrode comprising a transparent andelectrically conductive film or a semiconductor layer. Besides these,patterning by way of etching a transparent and electrically conductivefilm has been used in the production of displays such as liquid crystalpanels and the like.

Particularly, in the production of an amorphous silicon solar cell,there is known a manner of forming a transparent and electricallyconductive film on a light transmissive insulating substrate, etchingsaid transparent and electrically conductive film to have a desiredpattern suitable for a solar cell, forming an amorphous siliconsemiconductor layer as a photoelectric conversion layer on the patternedtransparent and electrically conductive film, and forming a back sideelectrode thereon. Besides this, there is also known a manner of formingan amorphous silicon semiconductor layer as a photoelectric conversionlayer on a metal substrate, forming a transparent and electricallyconductive film on said semiconductor layer, etching said transparentand electrically conductive film into a desired pattern, and forming agrid electrode as a collecting electrode on the patterned transparentand electrically conductive film. The latter is advantageous in that theresultant solar cell with the metal substrate can be readily processedinto a configuration having a bent portion, and electrochemicaltreatment for repairing a defective portion can be easily conductedbecause the substrate of the solar cell is comprised of a metal, andcontinuous film formation can be conducted.

A chemical etching method of selectively etching a transparent andelectrically conductive film formed on a substrate to have a desiredpattern in the production of a solar cell is known (see, JapaneseUnexamined Patent Publication No. 108779/1980 and U.S. Pat. No.4,419,530). Herein, such chemical etching method will be described.

In a first step, a photoresist (comprising a printing ink or resin) isformed on a transparent and electrically conductive film formed on asubstrate by means of printing technique such as silk screen printing orflexographic printing or a spinner, and the photoresist is subjected tolight exposure with a desired pattern, followed by subjecting todevelopment, whereby forming a desired positive resist pattern. In asecond step, a negative portion (excluding the positive resist pattern)comprising an exposed portion of the transparent and electricallyconductive film is etched with an etching solution containing ferricchloride or nitric acid so that a portion of the transparent andelectrically conductive film situated under the positive resist patternremains. In this case, the negative portion may be removed by means ofdry etching such as plasma etching so that the portion of thetransparent and electrically conductive film situated under the positiveresist pattern remains. In a third step, the positive resist pattern(comprising a cured photoresist pattern) remaining on the transparentand electrically conductive film is removed by eluting it with areleaser, peeling it, or manner of subjecting it to dry processing byplasma ashing, to thereby form a desired pattern of the transparent andelectrically conductive film.

There is also known an electrochemical etching method of etching atransparent and electrically conductive film used in liquid crystaldisplay or EL elements, wherein a transparent and electricallyconductive film is formed on a substrate, a resist pattern is contactedwith the surface of the transparent and electrically conductive film,the resultant is immersed in an electrolyte solution comprising anaqueous solution of HCl, followed by energization with an electriccurrent, whereby an exposed portion of the transparent and electricallyconductive film which is not covered by the resist pattern is patterned(see, Japanese Unexamined Patent Publication No. 290900/1987).

Incidentally, in the case of a thin film solar cell such as an amorphoussilicon solar cell, there is sometimes a problem in that the output ofthe voltage and electric current is markedly decreased due to shortcircuit defects created during the formation of its semiconductor layer.Such short circuit defects are usually created in the case where defectssuch as pinholes of electrically connecting the upper and lowerelectrodes to the semiconductor layer are present. There is a tendencythat such short circuit defects increase as the size of the solar cellis enlarged.

In view of this, in the case where a large area solar cell iscontinuously fabricated, for instance, by way of the so-calledroll-to-roll process, after the formation of the semiconductor layer ortransparent and electrically conductive film, it is necessary toeliminate the short circuit defects which are possibly present therein.

U.S. Pat. No. 4,166,918 discloses a method of removing short circuitdefects created during the fabrication process of a solar cell. Thismethod is to burn out the short circuit defects present in the solarcell by applying a reverse bias voltage of sufficient magnitude which isless than the breakdown voltage of the solar cell. Besides this, U.S.Pat. No. 4,729,970 discloses a method of passivating short circuitdefects in a solar cell by applying a reverse bias voltage to the solarcell in an electrolyte solution to remove a transparent and electricallyconductive film composed of ITO (Indium Tin Oxide.) or the like presentat the peripheries of the short circuit defects whereby passivating theshort circuit current current paths.

In general, in the case of fabricating a large sized solar cell, thereis often employed a manner of patterning the transparent and conductivefilm to have a desired size by subjecting the transparent and conductivefilm to etching treatment, removing the short circuit defects, andforming a collecting electrode. In accordance with this method, it ispossible to fabricate a large area thin film solar cell having a highperformance.

Now, any of the conventional patterning processes by way of the etchingtreatment is problematic in that it involves a variety of steps, i.e.,the formation of a positive resist pattern using a photoresist,exposure, development, etching, resist removal, and the like, and theyhave such problems as will be described below.

For the conventional chemical etching process, there are problems suchthat because the etching treatment is conducted in an electrolytesolution, the expansion or removal of a resist is liable to occur andtherefore, it is difficult to attain precise etching. In addition, it isnecessary to precisely control not only the temperature for the etchingsolution but also the period of time during which the etching treatmentis conducted.

For the conventional dry etching process, although it is possible toattain the patterning at a high precision, there are problems such thatthe treatment speed is slow and the throughput of the apparatus used islow, resulting in increased production cost, and in addition, since astrong oxidant is used, specific handling steps are necessary for it andalso the waste liquid.

For the conventional plasma ashing process, although it is free ofenvironmental pollution because no solution is used, there is a problemin that it cannot be employed for all the resists.

For the conventional electrochemical etching process, although it isadvantageous in that the temperature of the etching solution need not beas precisely controlled as in the case of the foregoing chemical etchingprocess, there are drawbacks such that to obtain a desired etchedpattern, a given resist pattern is necessary to be in close-contact withthe surface of a transparent and electrically conductive film formed ona substrate, no patterning can be conducted without the presence of aphotoresist, and the step of forming a pattern is essential.

In the case of patterning a transparent and electrically conductive filmformed on a stacked body comprising a plurality of thin film layersbeing stacked as a semiconductor layer for a photovoltaic element or thelike by means of the conventional chemical or electrochemical etchingprocess, there are such problems as will be described in the following.That is, when the treatment period of time with the etching solution islong, negative influences are liable to effect to the stacked body; andwhen the control of the temperature of the etching solution is notsufficiently conducted, defectively etched portions are liable to occur,resulting in electrical shorts or shunts the resulting photovoltaicelement. In the etching process using the resist, there are alsoproblems. When resist separation occurs during the etching process,overetching often occurs to unnecessarily etch a portion, resulting inexterior defects for a photovoltaic element and/or in making theresulting photovoltaic element to have inferior characteristics; and inthis case, there is a tendency of damaging a region or layer which isnot to be etched.

In the patterning process by the etching treatment by way of in thefabrication of a solar cell, patterning is usually conducted through aphotoresist or the like by means of the chemical etching process, dryetching process, or electrolytic etching. And in any case, a variety ofsteps, i.e., close-contact of a photoresist pattern to a solar cellsubstrate, etching, removal of the photoresist, rinsing, washing,drying, and the like are necessary. And after the completion of thesesteps, a further step of removing short circuit defects possibly presentin the solar cell substrate is often conducted.

In accordance with the roll-to-roll process, it is possible tocontinuously form a semiconductor layer, a transparent, electricallyconductive film and the like. However, in practice, it is difficult tomake the etching process and the short circuit defects-removing processso that they can be continuously conducted. And the etching stepsinvolve a variety of treatment steps as above described. Therefore, evenin the case where the roll-to-roll process is employed, there areproblems such that it is difficult to attain the fabrication of adefect-free solar cell at a high yield and with a reduced productioncost. In addition to this, because the etching process and the shortcircuit defects-removing process are separately conducted, in the caseof mass-producing a solar cell, there is an increased possibility inthat physical defects will arise.

Therefore, there is an increased demand for making an improvement in theconventional process for fabricating a solar cell so that the etchingprocess and the short circuit defects-removing process can becontinuously conducted.

Incidentally, the patterning in accordance with conventional etchingprocess using an etching apparatus is conducted, for example, in themanner shown in FIG. 1(a) through FIG. 1(h). Particularly, first, on atransparent and electrically conductive film 202 formed on a metalsubstrate 201 (see, FIG. 1(a)), a resist 204 is formed using a coatingdevice 203 (see, FIG. 1(b)), followed by drying using a drier (notshown). Thereafter, a mask pattern 205 is arranged on the resist 204,followed by subjecting the resultant to light exposure using a lightfilter 206 (see, FIG. 1(c)). Successively, development is conducted in avessel 207 containing a developer (see, FIG. 1(d)). After thedevelopment treatment, washing is conducted in a washing and rinsingvessel 208 (see, FIG. 1(e)), followed by drying. Thereafter, the body issubjected to etching treatment in an etching vessel 209 containing anetching solution (see, FIG. 1(f)), followed by removing the resist in aresist removing vessel 210, and successively followed by washing andthen drying (see, FIG. 1(g)), where the transparent and electricallyconductive film 202 on the metal substrate 201 is patterned as shown inFIG. 1(g). FIG. 1(h) is a schematic slant view illustrating a producthaving a desired pattern thus obtained.

In the above photolithography patterning process comprising theforegoing numerous steps, these steps are extremely difficult tocombine, and the respective instruments in which the respective stepsare conducted are also extremely difficult to integrate. If some ofthese steps could be designed so that they can be conducted in the sameinstrument, the instrument is unavoidably large. Hence, it is extremelydifficult to realize such a system that these numerous steps can becontinuously conducted to complete the patterning process within a shortperiod of time.

This situation is more or less the same also in the fabrication of asolar cell. Particularly, the etching process in the fabrication of asolar cell involves numerous steps similar to those described in theabove, and these numerous steps and the respective instruments in whichthe respective steps are conducted are extremely difficult to combine.Therefore, it is necessary to use separate instruments to conduct eachstep. In addition, it is extremely difficult to realize an apparatuswhich is capable of conducting both the etching process involving thenumerous steps and the short circuit defects-removing process in theapparatus. If the etching process and the short circuit defects-removingprocess could be designed so that they can be conducted in oneapparatus, the apparatus is unavoidably large. Hence, it is extremelydifficult to realize such a system that the etching process and theshort circuit defects-removing process can be continuously conductedwithin a short period of time.

SUMMARY OF THE INVENTION

A principal object of the present invention is to eliminate theforegoing problems in the prior art and to provide an etching processwhich has few, simple treatment steps0 and excels in selective etchingprecision, and which enables stably and efficiently conducting selectiveetching for an object to be treated by way of etching treatment such asa transparent and electrically conductive film or the like at animproved selective etching precision.

Another object of the present invention is to provide a highly reliablesemiconductor element such as a photovoltaic element including a solarcell or the like which is free of short circuit defects includingshunts, exterior defects and the like and which is free of a damage inthe non-etched region or layer.

A further object of the present invention is to provide a process whichenables continuously conducting a patterning process by way of etchingtreatment and a short circuit defects-removing process, wherein a highlyreliable semiconductor element such as a photovoltaic element includinga solar cell or the like can be efficiently produced at a high yield andwith a reduced production cost.

A further object of the present invention is to provide a process whichenables stably conducting a patterning process by way of etchingtreatment with an improved patterning precision, wherein a highlyreliable semiconductor element such as a photovoltaic element includinga solar cell or the like which is free of short circuit defectsincluding shunts, exterior defects and the like and which has a highperformance can be efficiently produced at a high yield and with areduced production cost.

A further object of the present invention is to provide an etchingapparatus which is small in size, simple and less expensive, which canshorten the treatment period, and which enables stably and efficientlyconducting selective etching for an object to be treated by way ofetching treatment, such as a transparent and electrically conductivefilm or the like, at high precision.

A further object of the present invention is to provide an etchingapparatus which is small in size and simple, which enables to conductboth a patterning process by way of etching treatment and a shortcircuit defects-removing process within a short time period in theapparatus. The apparatus also enables efficiently producing a highlyreliable semiconductor element such as a photovoltaic element includinga solar cell or the like which is free of short circuit defectsincluding shunts, exterior defects and the like and which has a highperformance which can be efficiently produced at a high yield and with areduced production cost.

A typical embodiment of the etching process according to the presentinvention is for etching a substrate having a portion to be etched,comprising a step of immersing said substrate in an electrolyte solutionsuch that said substrate serves as a negative electrode, a step ofarranging a counter electrode having a pattern corresponding to adesired pattern to be formed at said portion to be etched of saidsubstrate in said electrolyte solution so as to maintain an intervalbetween said counter electrode and said substrate, and a step ofapplying a direct current or a pulse current between said substrate andsaid counter electrode to etch said portion to be etched of saidsubstrate into a pattern corresponding to said pattern of said counterelectrode.

A typical embodiment of the process for producing a semiconductorelement according to the present invention comprises a step of immersinga substrate for a semiconductor element and having a portion comprisinga film to be etched in an electrolyte solution such that said substrateserves as a negative electrode, a step of arranging a counter electrodehaving a pattern corresponding to a desired pattern to be formed at saidportion to be etched of said substrate in said electrolyte solution soas to maintain a predetermined interval between said counter electrodeand said substrate, and a step of applying a direct current or a pulsecurrent between said substrate and said counter electrode to etch saidportion to be etched of said substrate into a pattern corresponding tosaid pattern of said counter electrode.

A typical embodiment of the etching apparatus according to the presentinvention comprises a substrate holding segment for holding a substratewith a portion to be etched, an electrolytic bath for maintaining anelectrolyte solution therein, a locomotive mechanism for moving thesubstrate holding segment in order to immerse the substrate held on thesubstrate holding segment in the electrolyte solution maintained in theelectrolytic bath, and a counter electrode holding segment for holding acounter electrode having a pattern corresponding to a desired etchingpattern to be formed at the portion to be etched of the substrate suchthat said counter electrode is positioned to oppose the substrate heldon the substrate holding segment.

In the present invention, no resist is formed on the side of a substratehaving a portion to be etched. Particularly, the principal feature ofthe present invention lies in that a given substrate having a portion tobe etched and a counter electrode shaped in a desired pattern arearranged in an electrolyte solution such that the counter electrode ispositioned to oppose the portion to be etched of the substrate,preferably in a state that the former is in close proximity to thelatter, and a direct current or a pulse current is applied between themto etch the portion to be etched of the substrate into a patterncorresponding to the pattern of the counter electrode. This makes itpossible to efficiently produce a highly reliable semiconductor devicesuch as a photovoltaic element including a solar cell or the like whichis free of short circuit defects including shunts, exterior defects andthe like and which has a high performance can be efficiently produced ata high yield and with a reduced production cost.

The above described etching apparatus enables practicing the processaccording to the present invention.

The portion to be etched in the present invention can include a film tobe etched which is disposed on a substrate and a film to be etched whichis disposed on a substrate through an intermediary such as asemiconductor layer, electrode, or the like.

The locomotive mechanism for moving the substrate holding segment in theforegoing etching apparatus according to the present invention serves toimmerse the substrate to be treated in and to take out the treatedsubstrate from the electrolyte solution. The locomotive mechanism may bedesigned to have a mechanism capable of moving up and down or rotatingto immerse the substrate to be treated in and to take out the treatedsubstrate from the electrolyte solution.

The foregoing etching apparatus according to the present invention maybe modified such that the substrate holding segment is pluralized andthe substrates held on the substrate holding segments can-becontinuously immersed in and taken out from the electrolyte solution byvirtue of the revolution of the locomotive mechanism.

Further, in the present invention, the substrate may be held on thesubstrate holding segment in a mechanical manner or by virtue of amagnetic force generated by a magnetic force generation means such as anelectromagnet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) through 1(g) are schematic cross-sectional views forexplaining a conventional etching process using photolithography.

FIG. 1(h) is a schematic slant view illustrating a product having anetched pattern obtained in accordance with the etching process shown inFIGS. 1(a) through 1(g).

FIG. 2(a) is a schematic diagram for explaining an example of an etchingprocess according to the present invention.

FIG. 2(b) is a schematic slant view for explaining an example of thepattern of a counter electrode used in the etching process shown in FIG.2(a).

FIG. 2(c) is a schematic slant view illustrating an example of apatterned product obtained in accordance with the etching process shownin FIG. 2(a).

FIG. 3(a) is a schematic cross-sectional view illustrating an example ofa semiconductor element produced according to the present invention.

FIG. 3(b) is a schematic plan view of the semiconductor element shown inFIG. 3(a).

FIG. 4 is a schematic diagram illustrating an example of an apparatussuitable for practicing the process according to the present invention.

FIG. 5 is a schematic diagram illustrating another example of anapparatus suitable for practicing the process according to the presentinvention.

FIG. 6 is a schematic cross-sectional view illustrating an example of asemiconductor element having short circuit defects.

FIG. 7 is a schematic cross-sectional view illustrating an example of arepaired semiconductor element in which short circuit defects areremoved.

FIG. 8 is a schematic flow chart showing an example of a process forproducing a semiconductor element in the present invention.

FIG. 9 is a schematic flow chart showing an example of a conventionalprocess by way of photolithography for producing a semiconductorelement.

FIG. 10 is a schematic diagram illustrating a further example of atreatment apparatus suitable for practicing the process according to thepresent invention.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The present inventors conducted extensive studies through experiments inorder to eliminate the foregoing problems found in the conventionalmethod for etching a given portion to be etched of a film usingreduction and dissolution phenomena based on electrochemical reactionand in order to find out an etching process which enables the efficientproduction of a desired, etched pattern at the portion to be etched ofthe film without those problems found in the prior art.

As a result, there was found an improved etching method which enablescontinuously etching an object to be etched in a desired pattern withimproved etching precision while desirably eliminating defects such asshort circuit defects in the same apparatus.

The present invention has been accomplished based on this finding.

The present invention lies in an improved etching process comprising thesteps of: immersing a substrate having a portion comprising a film to beetched in an electrolyte solution such that the substrate serves as anegative electrode; arranging a counter electrode such that the counterelectrode is positioned to oppose the substrate; and applying a directcurrent or a pulse current between the substrate and the counterelectrode to selectively etch the portion to be etched of the substrateinto a desired pattern by electrolytic reduction.

The present invention includes a process for producing a semiconductorelement comprising the steps of: (a) providing a semiconductor elementcomprising a semiconductor layer and a transparent and a transparent andelectrically conductive film formed in the named order on a substrate(comprising a metal body); (b) immersing the semiconductor element in anelectrolyte solution such that the substrate side of the semiconductorelement serves as a negative electrode; (c) arranging a counterelectrode such that the counter electrode is positioned to oppose thesemiconductor element; and (d) applying a direct current or a pulsecurrent between the substrate of the semiconductor element and thecounter electrode to selectively etch the transparent and electricallyconductive film of the semiconductor element into a desired pattern byelectrolytic reduction. If necessary, this process further comprises astep of applying a forward bias to the side of the substrate of thesemiconductor element to subject the transparent and electricallyconductive film present at the peripheries of defects, such as shortcircuit defects in the semiconductor element, to electrolytic reductionwhereby eliminating said defects.

According to the present invention, the formation of a highly preciseetched pattern comprising a transparent and electrically conductive filmcan be achieved.

Further, according to the present invention, desirable patterning athigh precision and elimination of short circuit defects can becontinuously conducted.

In the following, detailed description will be made of the presentinvention.

In general, as the transparent and electrically conductive film used inan amorphous solar cell or the like, a film excelling in transparencyagainst visible light and also in electrical conductivity such as a SnO₂film, In₂ O₃ film, ITO (In₂ O₃ +SnO₂) film, or the like is used. Thesetransparent and electrically conductive films may be formed by means ofvacuum evaporation, ionization evaporation, sputtering, CVD (chemical.vapor deposition), or spray coating.

In the case where these transparent and electrically conductive filmsare used in the amorphous solar cell, it is necessary for them to bepatterned for their predetermined, selected region by way of etchingtreatment. However, these transparent and electrically conductive filmsare insoluble in acids and bases and therefore, they are difficult toetch. Particularly, the reaction When they are chemically etched isslow, and because of this, in order to increase the reaction speed uponchemical etching, it is necessary to conduct the reaction a hightemperature.

On the other hand, in the case of the so-called electrochemical etchingprocess, as various electrolyte solutions can be used, the reactioninvolved in the etching proceeds at room temperature, and it is notnecessary to externally supply heat energy. In the electrochemicaletching process, nascent hydrogen generated on the cathode side upon theelectrolysis reduces a transparent and electrically conductive film todissolve in the electrolyte solution, whereby a given portion of thetransparent and electrically conductive film is removed.

In the present invention, the electrolyte used in the electrolytesolution is different depending upon the kind of the transparent andelectrically conductive film involved. Specific examples of theelectrolyte are sodium chloride, potassium chloride, aluminum chloride,zinc chloride, tin chloride, ferric chloride, sodium nitride, potassiumnitride, hydrochloric acid, nitric acid, and sulfuric acid.

The counter electrode used in the present invention may be one or morematerials selected from the group consisting of platinum, carbon, gold,stainless steel, nickel, copper and lead. Of these materials, gold,platinum, and carbon are the most appropriate because these arechemically stable and can be readily processed into a desired pattern.

In the present invention, it is possible to install an appropriategapping member between the substrate having a portion (for example,comprising a transparent and electrically conductive film) to be etchedand the counter electrode, for instance, such that the counter electrodeis pinched by the gapping member without being contacted with thegapping member, but the gapping member is contacted with the portion ofthe substrate to be etched. In this case, there can employed, forexample, an etching process as shown in FIGS. 2(a) and 2(b). FIG. 2(a)is a schematic lateral view illustrating a situation where substrate andthe counter electrode are arranged in close proximity to each otherthrough the gapping member in the electrolyte solution. FIG. 2(b) is aschematic slant view illustrating the arrangement of the counterelectrode and gapping member, viewed from the gapping member side.

FIG. 2(c) is a schematic slant view illustrating an example of apatterned transparent and electrically conductive film.

In FIGS. 2(a) through 2(c), reference numeral 101 indicates a substrate,reference numeral 102 a film (for example, a transparent andelectrically conductive film) to be etched, reference numeral 103 acounter electrode, reference numeral 104 a gapping member, referencenumeral 105 an electrolytic bath, reference numeral 106 an electrolytesolution, and reference numeral 107 a power source.

According to the manner shown in FIGS. 2(a) and (b), a desired etchedpattern can be obtained depending on the pattern of the counterelectrode exposed to the electrolyte solution.

In FIGS. 2(a) and 2(b), four counter electrodes are arranged toestablish a shape, and the patterning by way of etching treatment isconducted.

Detailed description will be made of the manner shown in FIGS. 2(a)through 2(c). The substrate 101 having the film 102 to be etched isimmersed in the electrolyte solution 106, and the substrate 101 side iselectrically connected to a negative electrode of the power source 107.The counter electrode 103 is positioned while maintaining apredetermined interval to the substrate through the gapping member 104,where the counter electrode 103 is not contacted with the gapping member104, but it is contacted with the film 102 of the substrate 101, and theelectrolyte solution 106 is always present between the film 102 of thesubstrate 101 and the counter electrode 103. But the interface betweenthe gapping member 104 and the film 102 of the substrate 101 is alwaysmaintained in a state free of the electrolyte solution 106. The counterelectrode 103 is electrically connected to a positive electrode of thepower source 107. By switching on the power source, a direct current orpulse current is applied between the counter electrode 103 and thesubstrate 101 to cause reduction reaction only at the surface of thefilm 102 situated to oppose the counter electrode 103, where the film102 is etched into a pattern corresponding to the pattern of the counterelectrode 103. Therefore, no mask is necessary to be formed on the film102 side. And by properly adjusting the width and thickness of thegapping member 104, the depth of the film 102 to be etched can beadjusted as desired in relation to the density of the current flow. Ingeneral, the width and thickness of the gapping member 104 is desired tobe adjusted in the range of from 0.1 mm to 2 mm. In the case where theinterval between the counter electrode 103 and the substrate 101 is toolarge, it is difficult to form a desirable etched pattern correspondingto the pattern of the counter electrode 103.

Further, by properly adjusting the period of time during which thedirect current is applied or/and the quantity of the direct currentapplied, or by applying the pulse current, the selectivity of thepatterning by way of the etching treatment can be controlled as desired.

The gapping member 104 is desirably a soft material having resistance tochemicals such as silicone rubber, silicone sponge, or the like.

In order to conduct the etching treatment together with the patterning,it is necessary to facilitate the electrolytic reduction reaction by theapplication of a direct current or pulse current as above-described. Theelectrolytic reduction reaction may be controlled by properly adjustingthe concentration of the electrolyte solution. However, the use of anelectrolyte solution with a high concentration often entails a problemof corroding a metallic portion of the apparatus used.

By properly adjusting the period of time during which the electriccurrent is applied or/and the quantity of the electric current applied,a desirable etched pattern can be formed even in the case of using anelectrolyte solution with a reduced concentration.

The formation of a uniform linear pattern can be attained in the casewhere the electric current applied is made constant.

Further, in the case where the electric current applied is in a pulseshape, the film (for example, comprising a transparent and electricallyconductive film) is step-wise etched in a thin film-like state inmultiple-steps, and because of this, a highly precise sharp linearpattern with no residue of the reduced film portion thereon can beobtained.

Now, the patterning precision of the film to be etched, such as atransparent and electrically conductive film, has a significant effecton the characteristics of a semiconductor device (including aphotosemiconductor device) such as a photovoltaic element (including asolar cell) or the like.

As an example of a semiconductor device prepared by conducting thepatterning according to the present invention, there can be mentioned anamorphous solar cell as shown in FIGS. 3(a) and 3(b).

Herein, it should be understood that this is only illustrative, and thepresent invention is effective also in amorphous solar cells having atransparent substrate. It should be also understood that the presentinvention is effective in other semiconductor devices (particularly,photosemiconductor devices) having a semiconductor layer such assingle-crystal series solar cells, polycrystal series solar cells, thinfilm polycrystal series solar cells, and microcrystal series solarcells.

FIG. 3(a) is a schematic cross-sectional view illustrating an amorphoussolar cell. FIG. 3(b) is a schematic plan view of the amorphous solarcell, viewed from the light incident side. In the amorphous solar cellshown in FIGS. 3(a) and 3(b), its constituent layer on the substrate ispatterned as required.

In FIGS. 3(a) and 3(b), reference numeral 300 indicates the entire ofthe amorphous solar cell, reference numeral 301 a substrate, referencenumeral 302 a lower electrode layer, reference numeral 303 asemiconductor layer, reference numeral 304 a transparent andelectrically conductive film with patterned portions 306, referencenumeral 305 a collecting electrode (or a grid electrode), referencenumeral 307 a positive side power outputting terminal, and 308 anegative side power outputting terminal.

The substrate 301 is usually an electrically conductive material in thecase of the amorphous solar cell, and it serves also as a back sideelectrode (or a lower electrode). The lower electrode layer 302 servesas one of the two electrodes for outputting a electric power generatedby the semiconductor layer 303.

The lower electrode layer 302 has a work function to provide an ohmiccontact against the semiconductor layer 303. The surface of the lowerelectrode layer 302 contacted with the semiconductor layer 303 may betextured so as to cause irregular reflection of light. The lowerelectrode layer 303 may be a metal body, metal alloy or transparent andelectrically conductive oxide. As such material, there can be mentioned,for example, Ag, Pt, AlSi, ZnO, In₂ O₃, ITO, and the like.

The semiconductor layer 303 may comprise a single cell structure whichcomprises a single cell unit with a pn or pin junction, comprising ann-type layer and a p-type layer being stacked or comprising an n-typelayer, an i-type layer, and a p-type layer being stacked; a double cellstructure which comprises a stacked body comprising two cell units beingstacked, each cell unit having a pn or pin junction and comprising ann-type layer and a p-type layer being stacked or comprising an n-typelayer, an i-type layer, and a p-type layer being stacked; or a triplecell structure which comprises a stacked body comprising three cellunits being stacked, each cell unit having a pn or pin junction andcomprising an n-type layer and a p-type layer being stacked orcomprising an n-type layer, an i-type layer, and a p-type layer beingstacked.

In order to obtain a large quantity of electric power, it is necessaryfor the solar cell to have a large area. However, as the area of thesolar cell is enlarged, there is a tendency for the photoelectricconversion efficiency decrease. A main reason for this lies in powerloss caused due to the electric resistance of the transparent andelectrically conductive film. Therefore, the active area of the solarcell is usually decided in relation with the current collectingefficiency of the collecting electrode 305.

However, by precisely patterning the transparent and electricallyconductive film, the active area of the solar cell can be increased asdesired, where an increase in the power outputted can be attainedaccordingly.

In the case where when upon patterning the transparent and electricallyconductive film by way of the etching treatment, when the transparentand electrically conductive film is not sufficiently etched as desiredto cause a breakage at the resulting patterned portion 306, leakagecurrent is generated from shunt portions other than the active area toreduce the photoelectric conversion efficiency. In addition, this defectin the etching of the transparent and electrically conductive film has anegative effect on the initial chracteristics of the solar cell, and itcontributes to the occurrence of shunts in reliability testing, wherethe solar cell has problems in the use in outdoors.

Therefore, it is necessary that a given portion of the transparent andelectrically conductive film which is to be etched is entirely removedupon the etching treatment.

In the following, selective etching apparatus suitable for practicingthe etching process according to the present will be describedinvention.

FIG. 4 is a schematic diagram illustrating an example of a selectiveetching apparatus suitable for practicing the etching process accordingto the present invention.

FIG. 5 is a schematic diagram illustrating another example of aselective etching apparatus suitable for practicing the etching processaccording to the present invention.

Description will be made of the apparatus shown in FIG. 4.

The apparatus shown in FIG. 4 is the type that the immersion of asubstrate (to be subjected to etching treatment) into an electrolytesolution is conducted in a rotary manner.

In FIG. 4, reference numeral 401 indicates an electrolytic bath,reference numeral 402 a substrate with a portion (for example,comprising a film) to be etched, reference numeral 403 an electrolytesolution, reference numeral 404 a counter electrode shaped in a desiredpattern, reference numeral 405 a lifting mechanism for moving thecounter electrode 404 up and down, reference numeral 406 a gappingmember, reference numeral 407 a substrate holding segment, referencenumeral 408 a rotary drum, reference numeral 409 a rotation axis,reference numeral 410 a substrate carrying mechanism, reference numeral411 a treated liquid removing mechanism, reference numeral 412 a powersource, reference numeral 413 a sequence controller, and referencenumeral 414 a carriage belt.

The electrolytic bath 401 is made of a material which excels in acidresistance and corrosion resistance, is light and can be readilyprocessed, such as vinyl chloride resin, acrylic resin, or the like.

The rotary drum 408 shown in FIG. 4 is shaped in a tetrahedral formhaving four faces each serving as the substrate holding segment 407 forholding the substrate 402 thereon. However, the shape of the rotary drum408 is not limited to this. The rotary drum 408 may be shaped in otherappropriate forms having five or more faces each capable of holding asubstrate 402 thereon such as a pentahedral form, hexahedral form, andthe like.

As shown in FIG. 4, the power source 412 is electrically connectedthrough its negative electrode to the rotation axis 409. The rotationaxis is electrically wired to an electrode fixed on the rear side ofeach face of the rotary drum 408 so that electric current flows to thesubstrate 402 held on said face of the rotary drum while being immersedin the electrolyte solution 403, where the substrate 402 serves as anegative electrode. The electric current supply electric system hereinis desirably designed to be turned on and off.

The counter electrode 404 is held on the lifting mechanism 405. Thegapping member 406 is positioned on the counter electrode 404 held onthe lifting mechanism 405. The counter electrode 404 is electricallyconnected to a positive electrode of the power source 412 through thelifting mechanism 405 and the sequence controller 413.

When the rotary drum 408 is rotated to bring the substrate 402 heldthereon in to the etching zone so that the substrate 402 is immersed inthe electrolyte solution 403 contained in the electrolytic bath 401, thecounter electrode 404 is positioned outside the radius of gyration ofthe rotary drum 408.

In the etching zone, immediately before electric current flows, thelifting mechanism 405 having the counter electrode 404 and the gappingmember 406 stacked in the named order thereon is lifted to contact thegapping member 406 with the portion to be etched of the substrate 402,and thereafter, the electric current flows between the counter electrode404 and the substrate 402 to etch the portion to be etched of thesubstrate. In this case, the quantity of the electric current flowingand the period of time during which the electric current flows arecontrolled as desired by means of the sequence controller 413. Theelectric current may be either direct current or pulse current. Afterthe completion of the etching treatment for the substrate 402, thelifting mechanism 405 having the counter electrode 404 and the gappingmember 406 thereon is returned to home position.

The substrate holding segment 407 is provided with an electromagnet (notshown) in order to fasten the substrate 402 positioned thereof by virtueof a magnetic force generated by the electromagnet, where to fix ordetach the substrate can be desirably conducted by turning on or off themagnetic force.

The apparatus shown in FIG. 4 may be provided with a mechanism includingthe electromagnet and a fixing plate, which operates such that uponfastening the substrate 402, the electromagnet closes the fixing platefrom the rear side of the substrate and upon detaching the substrate,the electromagnet retreats away from the fixing plate.

The treated liquid removing mechanism 411 serves to remove theelectrolyte solution 403 from the surface of the substrate 402 after theetching treatment for the substrate in order to prevent the electrolytesolution from being leaked to the outside. The removal of theelectrolyte solution is conducted by way of air-emission from anair-outlet or by means of a brush or blade.

The apparatus shown in FIG. 4 is markedly advantageous in that thesubstrate 402 to be treated can be continuously introduced to positionon each substrate holding segment 407 of the rotary drum 408 having atleast four faces as previously described, followed by the etchingtreatment; the stand-by, etching treatment, liquid removal, and take-outof a product can be continuously conducted without time loss; and theetching treatment of the substrate can be completed for an extremelyshort period of time.

Description will be made of the apparatus shown in FIG. 5.

The apparatus shown in FIG. 5 is the type that the immersion of asubstrate (to be subjected to etching treatment) into an electrolytesolution is conducted by moving the substrate down and up.

In FIG. 5, reference numeral 501 indicates an electrolytic bath,reference numeral 502 a substrate with a portion (for example,comprising a film), reference numeral 503 an electrolyte solution,reference numeral 504 a counter electrode shaped in a desired pattern,reference numeral 505 a gapping member, reference numeral 506 asubstrate holding segment provided at a mounting table, referencenumeral 507 a lifting mechanism for moving the substrate holding segment506 down and up, reference numeral 508 a treated liquid removingmechanism, reference numeral 509 a power source, reference numeral 510 asequence controller, and reference numeral 511 a carriage belt.

The lifting mechanism 507 comprises an air cylinder. It is moreeffective to use a ball bearing in combination with the air cylinder.

As shown in FIG. 5, the lifting mechanism 507 is connected to themounting table provided with the substrate holding segment 506 so thatthe immersion of the substrate 502 into the electrolyte solution 503,the etching treatment of the substrate, and the carriage of thesubstrate can be conducted for a short period of time by operating thelifting mechanism.

As shown in FIG. 5, the power source 509 is electrically connected tothe substrate 502 held on the substrate holding segment 506, and it isalso electrically connected to the counter electrode 504 through thesequence controller 510.

In the apparatus shown in FIG. 5, the etching treatment of the substrate502 is typically conducted as follows. The substrate holding segment 506having the substrate 502 held thereon moves down to immerse thesubstrate 502 into the electrolyte solution 503. Then, immediatelybefore electric current flows, the gapping member 506 situated on thecounter electrode 504 conducts with the portion to be etched of thesubstrate 502. Thereafter, the electric current flows between thecounter electrode 504 and the substrate 502 to etch the substrate asdesired. In this case, the quantity of the electric current and theperiod of time during which the electric current flows are controlled asdesired by means of the sequence controller 510. The electric currentmay be either direct current or pulse current.

The substrate holding segment 506 is provided with an electromagnet (notshown) in order to fasten the substrate 502 by virtue of a magneticforce generated by the electromagnet, so fixing or detaching thesubstrate can be desirably conducted by turning on or off the magneticforce.

The treated liquid removing mechanism 508 serves to remove theelectrolyte solution 503 from the surface of the substrate 502 after theetching treatment for the substrate in order to prevent the electrolytesolution from leaking to the outside. The removal of the electrolytesolution is conducted by way of air-emission from an air-outlet or bymeans of a brush or blade.

The apparatus shown in FIG. 5 is also markedly advantageous in that theintroduction of the substrate 502 into the electrolytic bath 501 isconducted in the plane direction and therefore, the amount of theelectrolytic solution required for the etching treatment of thesubstrate is small; and the scale of the apparatus can be miniaturized.

In the following, description will be made of the method of eliminatingshort circuit defects by way of electrolysis in the present invention,while referring to FIGS. 6 and 7.

FIG. 6 is a schematic cross-sectional view illustrating an example of asemiconductor element having short circuit defects. FIG. 7 is aschematic cross-sectional view illustrating an example of a repairedsemiconductor element in which said short circuit defects have beeneliminated.

In FIG. 6, because defects 1302 (or short circuit defects) are present,short-circuit current paths 1301 extend from a metal substrate 1303 to atransparent and electrically conductive film 1304 while crossing regionsof a semiconductor layer 1305. Herein, when forward bias is applied tothe substrate side of the semiconductor element in the presence of anelectrolyte solution, the involved portions of the transparent andelectrically conductive film 1304 are removed until they areelectrically insulated from the short-circuit current path 1301. Thatis, by eliminating the short-circuit current path 1301, the electricresistance of the shortcircuited portion is substantially increased atthe interface between the transparent and electrically conductive filmand the semiconductor region. The increase in the electric resistance ofthe shortcircuited portion provides a repaired semiconductor elementwhich is substantially free of the generation of short-circuit currentand has a good performance. Particularly, as shown in FIG. 7, theproblems of short circuit defects or shunts can be eliminated byremoving, of the transparent and electrically conductive film 1304stacked on the semiconductor layer 1305, its portions present at theperipheries of the defects 1302, whereby eliminating the short-circuitcurrent paths 1301.

For the forward bias applied, it is desired to apply a bias voltage of 2V to 10 V per one semiconductor element's substrate. As the electrolytesolution used, any electrolyte solutions may be optionally used as longas they have a function of removing a transparent and electricallyconductive film as well as in the case of the etching process by way ofelectrolysis.

The above described short circuit defects-eliminating process isadvantageous in that the same electrolyte solution can be used in boththe etching process and the short circuit defects-eliminating processand therefore, these two processes can be conducted in the sameelectrolyte solution; hence, these two processes can be continuouslyconducted in the same electrolytic bath; and this situation enablesmass-production of a semiconductor element such a photovoltaic element(including a solar cell) or the like having a reliable performance at ahigh yield.

FIG. 8 is a schematic flow chart showing an example of the processaccording to the present invention for producing a semiconductorelement. FIG. 9 is a schematic flow chart showing an example of aconventional process by way of photolithography for producing asemiconductor element. In comparison of the process according to thepresent invention shown in FIG. 8 with the conventional process shown inFIG. 9, it is clearly understood that the process according to thepresent invention is apparently simpler than the conventional process.

FIG. 10 is a schematic diagram illustrating an example of an apparatussuitable for practicing the process according to the present inventionin which the etching process and the short circuit defects-eliminatingprocess are continuously conducted.

In FIG. 10, reference numeral 1101 indicates an electrolytic bath,reference numeral 1102 a photovoltaic element comprising an electricallyconductive substrate and a stacked structure with at least asemiconductor layer and a transparent and electrically conductive filmdisposed on said substrate (this will be hereinafter referred to aselement substrate), reference numeral 1103 an electrolyte solution,reference numeral 1104 a first counter electrode shaped in a desiredpattern which is used for conducting etching treatment, referencenumeral 1105 a lifting mechanism for moving the first counter electrode1104 up and down (this will be hereinafter referred to as first counterelectrode lifting mechanism), reference numeral 1106 a second counterelectrode shaped in a desired pattern which is used for conducting shortcircuit defects-eliminating treatment, reference numeral 1107 asubstrate holding segment, reference numeral 1108 a rotary drum shapedin a multi-hedral form having a number of faces each serving as thesubstrate holding segment 1107, reference numeral 1109 a rotation axis,reference numeral 1110 a substrate carrying mechanism, reference numeral1111 a treated liquid removing mechanism, reference numeral 1112 a powersource for etching process (this will be hereinafter referred to asetching power source), reference numeral 1113 a power source for shortcircuit defects-eliminating process (this will be hereinafter referredto as defect elimination power source), reference numeral 1114 asequence controller, and reference numeral 1115 a carriage belt.

In the apparatus shown in FIG. 10, an element substrate 1102 ispositioned and held on each substrate holding segment 1107 of the rotarydrum 1108, and the rotary drum 1108 is rotated, where the elementsubstrates 1102 are successively immersed into the electrolyte solution1103, followed by subjecting to etching treatment and then to shortcircuit defects-eliminating treatment.

The electrolytic bath 1101 is made of a material which excels in acidresistance and corrosion resistance, is light and can be readilyprocessed, such as vinyl chloride resin, acrylic resin, or the like.

The rotary drum 1108 shown in FIG. 10 is shaped in a pentahedral formhaving five faces each serving as the substrate holding segment 1107 forholding the element substrate 1102 thereon. The shape of the rotary drum1108 is, however, not limited to this. The rotary drum 1108 may beshaped in other appropriate form, for instance, in a trihedral formparticularly in the case where the substrate holding segment 1107 isplane. However, the use of the rotary drum 1108 shaped in thepentahedral form as shown in FIG. 10 is markedly advantageous in thatthe introduction of the element substrate, stand-by, etching treatment,short circuit defects-removing treatment, liquid removal, and take-outof a product can be continuously conducted without time loss; and therotary drum 1108 can be miniaturized.

Alternatively, in the case where the element substrate 1102 can be bent,the rotary drum 1108 may be shaped in a round form so that the elementsubstrate can be held thereon in a state with a given curvature. In thiscase, both the first counter electrode 1104 and the second counterelectrode 1106 are necessary to be shaped to have a given curvature.

The electric system in the apparatus is desired to be designed such thatthe electrically conducting state of each substrate holding segment 1107of the rotary drum 1108 is turned on upon conducting the etchingtreatment and also upon conducting the short circuit defects-eliminatingtreatment. It is turned off when not conducting these treatments.

As shown in FIG. 10, the etching power source 1112 is electricallyconnected through its negative electrode and the sequence controller1114 to the rotation axis 1109. Similarly, the defect elimination powersource 1113 is electrically connected through its negative electrode andthe sequence controller 1114 to the rotation axis 1109. And the rotationaxis 1109 is electrically wired to the rear side of each face of therotary drum 1108 so that electric current flows to the element substrate1102 held on said face while being immersed in the electrolyte solution1103, where the element substrate 1102 serves as a negative electrode.The electric current supply electric system herein is desired to bedesigned such that it can be turned on and off.

The first counter electrode 1104 is held on the first counter electrodelifting mechanism 1105, and it is electrically connected to a positiveelectrode of the etching power source 1112 through the lifting mechanism1105. Similarly, The second counter electrode 1106 is held on a secondcounter electrode lifting mechanism, and it is electrically connected toa positive electrode of the defect elimination power source 1113 throughsaid lifting mechanism.

When the rotary drum 1108 is rotated, the first counter electrode 1104is positioned outside the radius of gyration of the rotary drum 1108,where immediately before electric current flows, the first counterelectrode is positioned in close proximity to the element substrate1102, and thereafter, the electric current flows between the firstcounter electrode 1104 and the element substrate 1102 to etch a givenportion of the element substrate 1102. In this case, the quantity of theelectric current and the period of time during which the electriccurrent flows are controlled as desired by means of the sequencecontroller 1114. The electric current may be either direct current orpulse current.

The first counter electrode 1104 is shaped in a desired pattern asabove-described. In the etching treatment, electrochemical reaction iscaused by converging the electric current to the electrode. It isdesired for the first counter electrode to function to always attain auniform patterning line. In view of this, the first counter electrode1104 is desired to be constituted by a material having high durabilitysuch as platinum, gold, or carbon.

In the short circuit defects-eliminating treatment, the second counterelectrode 1106 is positioned so as to maintain a predetermined parallelinterval to the element substrate 1102, and a given forward bias isapplied to the element substrate 1102 side, whereby to eliminate shortcircuit defects present in the element substrate is conducted. In thiscase, as well as in the case of the etching treatment, the quantity ofthe electric current and the period of time during which the electriccurrent flows are controlled as desired by means of the sequencecontroller 1114.

It is possible to install a mechanism capable of adjusting the intervalbetween the second counter electrode 1106 and the element substrate 1102on the side of the second counter electrode 1106.

The second counter electrode 1106 may be constituted by platinum,carbon, gold, stainless steel, nickel, copper, or lead. In the casewhere the second counter electrode 1106 is required to excelparticularly in dissolution resistance, it is desired to be constitutedby platinum which is chemically stable and can be readily processed intoa desired pattern.

The substrate holding segment 1107 is provided with an electromagnet(not shown) in order to fasten the element substrate 1102 positionedthereof by virtue of a magnetic force generated by the electromagnet,where to fix or detach the substrate can be desirably conducted byturning on or off the magnetic force.

The apparatus shown in FIG. 10 may be provided with a mechanismincluding the electromagnet and a fixing plate, which operates such thatupon fastening the element substrate 1102, the electromagnet closes thefixing plate from the rear side of the element substrate and upondetaching the substrate, the electromagnet retreats away from the fixingplate.

The treated liquid removing mechanism 1111 serves to remove theelectrolyte solution 1103 from the surface of the element substrate 1102after the etching treatment and short circuit defects-eliminatingtreatment for the element substrate in order to prevent the electrolytesolution from being leaked to the outside. The removal of theelectrolyte solution is conducted by way of air-emission from anair-outlet or by means of a brush or blade.

The apparatus shown in FIG. 10 is markedly advantageous in that theelement substrate 1102 to be treated can be continuously introduced toposition on each substrate holding segment 1107 of the rotary drum 1108,followed by the etching treatment and then the short circuitdefects-eliminating treatment; the introduction of the element substrateto be treated, stand-by, etching treatment, short circuitdefects-eliminating treatment, liquid removal, and take-out of a productcan be continuously conducted without time loss; and the etchingtreatment and short circuit defects-eliminating treatment of the elementsubstrate can be continuously completed for an extremely short period oftime.

In the following, the present invention will be described in more detailwith reference to examples which are not intended to restrict the scopeof the present invention.

EXAMPLE 1

In this example, there were prepared 100 p-i-n junction single cell typeamorphous solar cells having the constitution shown in FIGS. 3(a) and3(b) while patterning their transparent and electrically conductivefilms using the etching apparatus shown in FIG. 4 in the followingmanner.

1. Preparation of photovoltaic element:

There was first provided a stainless steel SUS430BA plate (trademarkname) as the substrate 301. The stainless steel plate was degreased andthen well washed.

On the stainless steel plate thus well cleaned as the substrate 301,there was formed a two-layered lower electrode layer 302 comprising a4000 Å thick Ag film and a 4000 Å thick ZnO film by means of theconventional sputtering process. Succesively, on the lower electrodelayer 302, there was formed a p-i-n junction single cell typephotoelectric conversion semiconductor layer 303 with a n-i-p structurecomprising a 250 Å thick n-type layer/a 4000 Å thick i-type layer/a 100Å thick p-type layer being stacked in the named order from the substrateside by means of the conventional RF plasma CVD process, wherein ann-type a-Si film as the n-type layer was formed from a mixture of SiH₄gas, PH₃ gas and H₂ gas; an i-type a-Si film as the i-type layer wasformed from a mixture of SiH₄ gas and H₂ gas; and a p-type μc-Si film asthe p-type layer was formed from a mixture of SiH₄ gas, BF₃ gas and H₂gas. Then, on the photoelectric conversion semiconductor layer 303,there was formed a 700 Å thick In₂ O₃ film as the transparent andelectrically conductive film 304 (having a function of preventing theoccurrence of light reflection) by means of the conventional heatresistance evaporation process wherein an In-source was evaporated at190° C. in an O₂ atmosphere. Thus, there was obtained a photovoltaicelement.

The resultant photovoltaic element was cut through its substrate toobtain 100 photovoltaic element of 31 cm×31 cm in size (thesephotovoltaic elements will be hereinafter referred to as elementsubstrates).

2. Patterning treatment (etching treatment) for the transparent andelectrically conductive film of the photovoltaic element:

The patterning treatment was conducted using the etching apparatus shownin FIG. 4.

One of the 100 element substrates obtained in the above step 1 wasplaced on one of the two carriage belts 414 (made of a rubber) of theetching apparatus shown in FIG. 4 such that the substrate of the elementsubstrate was contacted with the surface of the carriage belt 414. Thesubstrate carrying mechanism 410 (provided with a suction pat) washorizontally moved to reach the carriage belt 414 having the elementsubstrate placed thereon and to take up the element substrate from thecarriage belt 414. Then, the substrate carrying mechanism 410 having theelement substrate was horizontally returned and it was lowered to unloadthe element substrate (402) such that it was positioned on the substrateholding segment 407 of the tetrahedral-shaped rotary drum 408. Afterthis, the substrate carrying mechanism 410 was returned to homeposition.

Incidentally, on the carriage belt 414 from which the element substrate(402) was taken up, the following element substrate was placed to standby for the next treatment turn.

After the element substrate (402) was positioned on the substrateholding segment 407 of the tetrahedral-shaped rotary drum 408, theelectromagnet (not shown in the figure, but previously explained) wasraised to fasten the element substrate (402) held on the substrateholding segment 407 by virtue of a magnetic force generated by theelectromagnet. Thereafter, the rotary drum 408 was rotated to arrive theelement substrate (402) held on the substrate holding segment 407 in theetching treatment zone, where the element substrate (402) held on thesubstrate holding segment 407 was immersed in the electrolyte solution403 contained in the electrolytic bath 401. As the electrolyte solution403, an electrolyte solution containing 8 wt. % of a hexahydrate ofaluminum chloride as an electrolyte dissolved therein and having anelectric conductivity of 65.0 mS/cm² was used, and it was maintained at25° C. Herein, the revolution of the rotary drum 408 was suspended.

Incidentally, as the rotary drum 408 was rotated as above-described, thesubstrate carrying mechanism was operated to take up the followingelement substrate from the carriage belt 414 and to unload it such thatit was positioned on the following substrate holding segment 407, andthe element substrate was fastened so that it was surely held on thesubstrate holding segment, in the same manner as in the case of theformer element substrate (402). Thereafter, on the carriage belt 414from which the latter element substrate was taken up, the followingelement substrate was placed to stand by for the next treatment turn.

Now, when the element substrate (402) was arrived in the etchingtreatment zone and it was immersed in the electrolyte solution, thelifting mechanism 405 having the counter electrode 404 and the gappingmember 406 comprising a 1 mm thick silicone rubber member stacked in thenamed order on the surface thereof was lifted to contact the gappingmember 406 with the transparent and electrically conductive film of theelement substrate (402) held on the substrate holding segment 407.

Herein, as the counter electrode 404, there was used a patterned counterelectrode comprising a platinum plate with a 1 mm thick silicone rubberfilm bonded to cover the entire of a surface of said platinum plate andhaving a square groove of 30 cm×30 cm in size and 0.5 mm in width formedthrough the silicone rubber film such that the platinum plate is exposedin the square groove and the remaining rear and side faces of theplatinum plate being insulated by an insulating film.

Then, the power source 412 was switched on to apply a direct current of25 A between the counter electrode 404 and the element substrate (402)for 0.5 second while controlling by the sequence controller 413. Afterthis, the lifting mechanism 405 was returned to home position togetherwith the gapping member 406 and the counter electrode 404.

Then, the rotary drum 408 was again rotated, during which when theelement substrate (402) held on the substrate holding segment 407 passedby the treated liquid removing mechanism 411, air was sprayed againstthe element substrate (402) by operating the treated liquid removingmechanism to remove the electrolyte solution deposited on the elementsubstrate.

Thereafter, when the substrate holding segment 407 (having the elementsubstrate (402) free of the electrolyte solution held thereon) of therotary drum 408 was returned to the starting position, the revolution ofthe rotary drum 408 was suspended, and the electromagnet was removedfrom the element substrate.

Successively, the substrate carrying mechanism 410 was lowered to reachthe element substrate (402) on the substrate holding segment 407 of therotary drum 408 to take up the element substrate (402) from the rotarydrum 408 and to unload the element substrate (402) on the other carriagebelt 414. This carriage belt was operated to carry the element substrate(402) outside the apparatus. Thus, there was obtained a photovoltaicelement having a patterned transparent and electrically conductive film.The time required for the patterning treatment was 10 seconds.

The successive element substrates each held on the substrate holdingsegment 407 were continuously treated in the same manner as in the caseof the above element substrate (402).

By this, the 100 photovoltaic elements obtained in the above step 1 werecontinuously treated to obtain 100 patterned photovoltaic elementshaving a patterned transparent and electrically conductive film.

3. Preparation of solar cell:

Using the 100 patterned photovoltaic elements obtained in the above step2, 100 solar cells were prepared in the following manner.

Each photovoltaic element was well washed with pure water, followed bydrying.

On the patterned transparent and electrically conductive film 304 of thephotovoltaic element thus cleaned, an Ag-paste was applied by means ofscreen printing, followed by drying, to thereby form a grid electrode asthe collecting electrode 305. A copper tub as the positive side poweroutputting terminal 307 was connected to the grid electrode as thecollecting electrode 305 using an Ag-paste, and a tin foil tape as thenegative side power outputting terminal 308 was connected to the rearside of the substrate 301 using a solder. Thus, there was obtained asolar cell. In this way, there were obtained 100 solar cells.

EVALUATION

For each of the resultant solar cells, evaluation was conducted asfollows.

(1). Evaluation was conducted with respect to initial characteristics inthe following manner.

The voltage-current characteristics (V-I characteristics) in dark statewere measured by the conventional V-I characteristics measuring manner,and based on the gradient near the origin in the resultant curve, therewas obtained a shunt resistance. A mean value among the shuntresistances obtained for the 100 solar cells was calculated to be 80kΩ.cm². All the solar cells were found to be free of a shunt created.

(2). Evaluation was conducted with respect to photoelectric conversionefficiency in a manner of measuring solar cell characteristics of eachsolar cell using a solar cell simulator having a pseudo sunlight sourcewith an AM 1.5 global sunlight spectra and capable of providing a lightquantity of 100 mW/cm² (produced by SPIRE Company) and obtaining aphotoelectric conversion efficiency based on the measured solar cellcharacteristics. As a result, all the solar cells were found to have asatisfactory photoelectric conversion efficiency in the range of7.0±0.2%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result, the 100solar cells were almost found to be free of disconnection anddefectively etched portion and to have a uniformly etched line. Theyield was found to be 95%.

(3). Using some of the 100 solar cells and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For each of the resultant solar cellmodules, a reliability test was conducted based on the temperature andhumidity cycle test A-2 prescribed in the JIS C8917 concerning theenvironmental test and endurance test for crystalline series solar cellmodules. Particularly, the solar cell module was placed in athermo-hygrostat capable of optionally controlling the relatedtemperature and humidity, where the solar cell module was subjected toalternate repetition of a cycle of exposing to an atmosphere of -40° C.for an hour and a cycle of exposing to an atmosphere of 85° C./85%RH foran hour, 20 times. Thereafter, using the solar cell simulator describedin the above (2), its photoelectric conversion efficiency was examinedin the same manner as in the above (2). The examined photoelectricconversion efficiency was compared with that obtained in the above (2)to observe a deterioration proportion in terms of the photoelectricconversion efficiency for each solar cell module. A mean value among thedeterioration proportions obtained for all the solar cell modules wascalculated to be about 2.0% which is satisfactory.

From the evaluated results above described, the following facts areunderstood. That is, the patterning precision by the foregoing etchingtreatment is good, and all the solar cells produced by way of thepatterning by the foregoing etching treatment are good in initialcharacteristics and highly reliable. In addition, it is understood thatthe process according to the present invention enables mass productionof a highly reliable solar cell without conducting any provisional stepbefore and after the etching treatment by way of electrolysis, and at animproved treatment speed and with a short period of time required forthe etching treatment.

COMPARATIVE EXAMPLE 1

In this comparative example, there were prepared 100 p-i-n junctionsingle cell type amorphous solar cells having the constitution shown inFIGS. 3(a) and 3(b) while patterning their transparent and electricallyconductive film by the conventional patterning process by way ofphotolithography and electrolysis etching.

1. Preparation of photovoltaic element:

In accordance with the procedures for the preparation of a photovoltaicelement, described in the step 1 (preparation of photovoltaic element)of Example 1, there were prepared 100 photovoltaic elements.

2. Patterning treatment by way of photolithography and electrolysisetching for the transparent and electrically conductive film of thephotovoltaic element:

The patterning treatment for the transparent and electrically conductivefilm of each of the photovoltaic elements obtained in the above step 1was conducted in the accordance with the conventional patterning processpreviously described with reference to FIGS. 1(a) through 1(h).

That is, for each photovoltaic element, on the transparent andelectrically conductive film thereof, a resist was formed by applying acoating composition comprising a photosensitive resin and subjecting todrying. Then, a mask pattern having a square pattern of 30 cm×30 cm insize and 0.5 mm in width was arranged on the resist, followed bysubjecting to irradiation of ultraviolet rays. The resultant wasdeveloped using a developer, followed by washing and rinsing, and thenfollowed by drying, to thereby obtain a patterned product (hereinafterreferred to as element substrate). The element substrate was subjectedto etching treatment in a conventional etching vessel containing acounter electrode and an etching solution comprising an electrolytesolution containing 8 wt. % of a hexahydrate of aluminum chloride as anelectrolyte dissolved therein and having an electric conductivity of65.0 mS/cm² (which is the same as in Example 1), followed by washing andthen drying. Thereafter, the remaining photomask on the elementsubstrate was eluted with ethanol to remove, followed by washing andthen drying. Thus, there was obtained a photovoltaic element having apatterned transparent and electrically conductive film.

By repeating the above procedures, there were obtained 100 patternedphotovoltaic elements having a patterned transparent and electricallyconductive film.

3. Preparation of solar cell:

Using the 100 patterned photovoltaic elements obtained in the above step2, 100 solar cells were prepared in accordance with the proceduresdescribed in the step 3 (preparation of solar cell) in Example 1.

EVALUATION

The resultant 100 solar cells were evaluated in the same evaluationmanner as in Example 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1. As aresult, 10 of the 100 solar cells were found to have a shunt resistanceof 10 kΩ.cm².

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the same manner as in Example 1.

As a result, all the solar cells were found to have a photoelectricconversion efficiency varied in the range of 5.3±1.8%. And some of thesolar cells were found to have shunts created.

And for each solar cell, the patterned portions were examined by meansof a microscope. As a result, the solar cells were almost found to havedisconnections. It is considered that this disconnection problemoccurred due to insufficiency in the removal of the photomask upon thepatterning by the irradiation of ultraviolet rays.

And for the solar cells having a inferior photoelectric conversionefficiency and shunts created, they were found to have an unevenpatterned line with an undesirably large width. The reason for this isconsidered such that the adhesion between the photoresist film and thetransparent and electrically conductive film was insufficient and theportion of the transparent and electrically conductive film situated onthe counter electrode side was not patterned, and because of this, theline of electric force could not be desirably controlled to result incausing side etching or overetching.

EXAMPLE 2

In this example, there were prepared 100 p-i-n Junction triple cell typeamorphous solar cells having the constitution shown in FIGS. 3(a) and3(b) while patterning their transparent and electrically conductivefilms using the etching apparatus shown in FIG. 4 in the followingmanner.

1. Preparation of photovoltaic element:

There was first provided a stainless steel SUS430BA plate (trademarkname) as the substrate 301. The stainless steel plate was degreased andthen well washed.

On the stainless steel plate thus well cleaned as the substrate 301,there was formed a two-layered lower electrode layer 302 comprising a4000 Å thick Ag film and a 4000 Å thick ZnO film by means of theconventional sputtering process. Successively, on the lower electrodelayer 302, there was formed a p-i-n junction triple cell typephotoelectric conversion semiconductor layer 303 with an-i-p/n-i-p/n-i-p structure having a bottom cell comprising a 250 Åthick n-type layer/a 1050 Å thick i-type layer/a 100 Å thick p-typelayer, a middle cell comprising a 600 Å thick n-type layer/a 1450 Åthick i-type layer/a 100 Å thick p-type layer, and a top cell comprisinga 100 Å thick n-type layer/a 1000 Å thick i-type layer/a 100 Å thickp-type layer being stacked in the named order from the substrate side bymeans of the conventional microwave plasma CVD, wherein an n-type a-Sifilm as the n-type layer was formed from a mixture of SiH₄ gas, PH₃ gasand H₂ gas; an i-type a-Si film as the i-type layer was formed from amixture of SiH₄ gas and H₂ gas; and a p-type μc-Si film as the p-typelayer was formed from a mixture of SiH₄ gas, BF₃ gas and H₂ gas. Then,on the photoelectric conversion semiconductor layer 303, there wasformed a 730 Å thick ITO film as the transparent and electricallyconductive film 304 (to prevent light reflection) by means of theconventional sputtering process wherein a target comprising In and Snwas sputtered at 170° C. in an O₂ atmosphere. Thus, there was obtained aphotovoltaic element.

The resultant photovoltaic element was cut through its substrate toobtain 100 photovoltaic elements of 31 cm×31 cm in size.

2. Patterning treatment (etching treatment) for the transparent andelectrically conductive film of the photovoltaic element:

For the 100 photovoltaic elements obtained in the above step 1, thepatterning treatment was conducted in the same manner as in the step 2of Example 1.

Particularly, the 100 photovoltaic elements obtained in the above step 1were successively introduced into the etching apparatus shown in FIG. 4and they were continuously subjected to patterning treatment in the samemanner as in the step 2 of Example 1, to thereby obtain 100 patternedphotovoltaic elements having a patterned transparent and electricallyconductive film.

3. Preparation of solar cell:

Using the 100 patterned photovoltaic elements obtained in the above step2, 100 solar cells were prepared in accordance with the proceduresdescribed in the step 3 (preparation of solar cell) in Example 1.

EVALUATION

The resultant 100 solar cells were evaluated in the same evaluationmanner as in Example 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1.

As a result, the mean value among the shunt resistances obtained for the100 solar cells was found to be 90 kΩ.cm². All the solar cells werefound to be free of a shunt.

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the same manner as in Example 1.

As a result, all the solar cells were found to have a satisfactoryphotoelectric conversion efficiency in the range of 9.0±0.2%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result, the 100solar cells were found to be almost free of disconnection anddefectively etched portions and to have a uniformly etched line. Theyield was found to be 95%.

(3). Using some of the 100 solar cells, and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For the resultant solar cell modules,reliability testing was conducted in the same manner as in Example 1. Asa result, the mean value among the deterioration proportions obtainedfor all the solar cell modules was found to be about 2.1% which issatisfactory.

From the results above-described, the following facts are understood.That is, the patterning precision by the foregoing etching treatment is,good and all the solar cells produced by way of the patterning by theforegoing etching treatment are good in initial characteristics andhighly reliable. In addition, it is understood that the processaccording to the present invention enables mass-production of a highlyreliable solar cell without conducting any provisional step before andafter the etching treatment by way of electrolysis, and at an improvedtreatment speed and with a short period of time required for the etchingtreatment.

EXAMPLE 3

In this example, there were prepared 100 p-i-n junction single cell typeamorphous solar cells having the constitution shown in FIGS. 3(a) and3(b), while patterning their transparent and electrically conductivefilms using the etching apparatus shown in FIG. 5 in the followingmanner.

1. Preparation of photovoltaic element:

In accordance with the procedures for the preparation of a photovoltaicelement, described in the step 1 (preparation of photovoltaic element)of Example 1, there were prepared 100 p-i-n junction single cell typephotovoltaic elements (these photovoltaic elements will be hereinafterreferred to as element substrates).

2. Patterning treatment for the transparent and electrically conductivefilm of the photovoltaic element:

The patterning treatment was conducted using the etching apparatus shownin FIG. 5.

One of the 100 element substrates obtained in the above step 1 wasplaced on one of the two carriage belts 511 (made of a rubber) of theetching apparatus shown in FIG. 5 such that the substrate thereof wascontacted with the surface of the carriage belt 511. The liftingmechanism 507 provided with the mounting table having the substrateholding segment 506 was horizontally moved to reach the carriage belt511 having the element substrate placed thereon and to take up theelement substrate on the carriage belt 511 by virtue of a magnetic forcegenerated by energizing the electromagnet (not shown) provided at thesubstrate holding segment 506 such that the element substrate (502) waspositioned on the substrate holding segment 506. After this, the liftingmechanism 507 was horizontally returned and it was lowered to immersethe substrate holding segment 506 having the element substrate (502)held thereon into the electrolyte solution 503 contained in theelectrolytic bath 501. As the electrolyte solution 503, an electrolytesolution containing 10 wt. % of a hexahydrate of potassium chloride asan electrolyte dissolved therein and having an electrical conductivityof 50.0 mS/cm² was used, and it was maintained at 25° C. Successively,the lifting mechanism 507 was further lowered so that the transparentand electrically conductive film of the element substrate (502) wascontacted with the gapping member 505 comprising a 1 mm thick siliconerubber member stacked on the counter electrode 504.

As the counter electrode 504 there was used a patterned counterelectrode comprising a platinum plate with a 1 mm thick silicone rubberfilm bonded to cover the entire surface of said platinum plate andhaving a square groove of 30 cm×30 cm in size and 0.5 mm in width formedthrough the silicone rubber film such that the platinum plate is exposedin the square groove. The remaining rear and side faces of the platinumplate are insulated by an insulating film.

Then, the power source 509 was switched on to apply a direct current of30 A between the counter electrode 504 and the element substrate (502)for 0.4 second while being controlled 3. by the sequence controller 510.After this, the lifting mechanism 507 was lifted. When the elementsubstrate (502) held on the substrate holding segment 506 of themounting table passed by the treated liquid removing mechanism 508, airwas sprayed against the element substrate (502) by operating the treatedliquid removing mechanism to remove the electrolyte solution depositedon the element substrate.

After the lifting mechanism 507 was lifted until the element substrate(502) held on the substrate holding segment 506 of the mounting tablewas situated above the electrolytic bath 501, the lifting mechanism washorizontally moved to reach the other carriage belt 511, where themagnetic force of fixing the element substrate (502) to the surface ofthe substrate holding segment 506 of the mounting table was unloaded onthe carriage belt 511 by turning off the electromagnet. This carriagebelt was operated to carry the treated element substrate outside theapparatus. Thus, there was obtained a photovoltaic element having apatterned transparent and electrically conductive film. The timerequired for the patterning treatment was 10 seconds.

The above procedures were continuously repeated. By this, the 100photovoltaic elements obtained in the above step 1 were continuouslytreated to obtain 100 patterned photovoltaic elements having a patternedtransparent and electrically conductive film.

3. Preparation of solar cell:

Using the 100 patterned photovoltaic elements obtained in the above step2, 100 solar cells were prepared in accordance with the proceduresdescribed in the step 3 (preparation of solar cell) in Example 1.

EVALUATION

The resultant 100 solar cells were evaluated in the same evaluationmanner as in Example 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1.

As a result, the mean value among the shunt resistances obtained for the100 solar cells was found to be 85 Ω.cm². From this, it was found thatall the solar cells are free of the occurrence of a shunt.

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the manner as in Example 1.

As a result, all the solar cells were found to have a satisfactoryphotoelectric conversion efficiency in the range of 7.1±0.3%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result, the 100solar cells were found to be almost free of disconnection anddefectively etched portions and to have a uniformly etched line. Theyield was found to be 97%.

(3). Using some of the 100 solar cells and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For the resultant solar cell modules,reliability testing was conducted in the same manner as in Example 1. Asa result, the mean value among the deterioration proportions obtainedfor all the solar cell modules was found to be about 1.8%, which issatisfactory.

From the results above-described, the following facts are understood.That is, the patterning precision by the foregoing etching treatment isgood, and all the solar cells produced by way of the patterning by theforegoing etching treatment are good in initial characteristics andhighly reliable. In addition, it is understood that the processaccording to the present invention enables mass-production of a highlyreliable solar cell without conducting any provisional step before andafter the etching treatment by way of electrolysis, and at an improvedtreatment speed and with a short period of time required for the etchingtreatment.

EXAMPLE 4

In this example, as an example of etching a metallic electricallyconductive film, the patterning for a distributing circuit on a waferused in an IC was conducted as follows.

A 1000 Å thick Ti--W metal layer was deposited on a wafer by theconventional sputtering process, followed by depositing a 1 μm thickaluminum metal layer on the Ti--W metal layer by the conventionalsputtering process, to obtain an element body. In this way, there wereobtained a plurality of element bodies.

The resultant element bodies were subjected to patterning treatment inaccordance with the patterning procedures using the etching apparatusshown in FIG. 4, described in the step 2 of Example 1 except forreplacing the counter electrode 404 used in Example 1 by a counterelectrode obtained by modifying the counter electrode 404 to have apattern corresponding to a desired distributing circuit pattern, whereinthe element bodies were continuously subjected to etching treatment inthe same manner as in Example 1 to etch their aluminum metal layers.patterned element bodies have a pattern corresponding to thedistributing circuit pattern of the counter electrode were obtained.

For each of the resultant patterned element bodies, the patternedportions were examined by means of a microscope. As a result, all thepatterned element bodies were found to free of disconnections anddefectively etched portions. The distributing circuit pattern of each ofthe resultant patterned element bodies, its electric behavior wasexamined. As a result, no anomalous electric behavior was observed forall the patterned element bodies.

Based on the above results, it is understood that the patterningprecision by the etching treatment according to the present invention isgood and that the present invention enables efficient mass-production ofa highly reliable distributing circuit pattern for ICs.

EXAMPLE 5

In this example, there were prepared 100 p-i-n junction single cell typeamorphous solar cells having the constitution shown in FIGS. 3(a) and3(b) while patterning their transparent and electrically conductivefilms and eliminating short circuit defects possibly created in thefabrication of said amorphous solar cell, using the apparatus shown inFIG. 10 capable of continuously conducting the etching process and theshort circuit defects-eliminating process, in the following manner.

1. Preparation of photovoltaic element:

In accordance with the procedures for the preparation of a photovoltaicelement, described in the step 1 (preparation of photovoltaic element)of Example 1, there were prepared 100 photovoltaic elements (thesephotovoltaic elements will be hereinafter referred to as elementsubstrates).

2. Etching treatment and short circuit defects-eliminating treatment:

The etching treatment and short circuit defects-eliminating treatmentwere continuously conducted using the apparatus shown in FIG. 10.

One of the 100 element substrates obtained in the above step 1 wasplaced on one of the two carriage belts 1115 (made of a rubber) of theapparatus shown in FIG. 10 such that the substrate thereof was contactedwith the surface of the carriage belt 1115. The substrate carryingmechanism 1110 (provided with a suction pat) was horizontally moved toreach the carriage belt 1115 having the element substrate placed thereonand to take up the element substrate from the carriage belt 1115. Then,the substrate carrying mechanism 1110 was horizontally returned and itwas lowered to unload the element substrate (1102) such that it waspositioned on the substrate holding segment 1107 of thepentahedral-shaped rotary drum 1108.

Incidentally, on the carriage belt 1115 from which the element substrate(1102) was taken up, the following element substrate was placed tostand-by for the next treatment.

After the the element substrate (1102) was positioned on the substrateholding segment 1107 of the rotary drum 1108 as above described, thesubstrate carrying mechanism 1110 was returned to home position.Thereafter, the electromagnet (not shown in the figure, but previouslyexplained) was raised to fasten the element substrate (1102) held on thesubstrate holding segment 1107 by virtue of a magnetic force generatedby the electromagnet. Thereafter, the rotary drum 1108 was rotated tobring the element substrate (1102) held on the substrate holding segment1107 to the etching treatment zone, where the element substrate (1102)held on the substrate holding segment 1107 was immersed in theelectrolyte solution 1103 contained in the electrolytic bath 1101. Asthe electrolyte solution 1103, an electrolyte solution containing 8 wt.% of a hexahydrate of aluminum chloride as an electrolyte dissolvedtherein and having an electric conductivity of 65.0 mS/cm² was used, andit was maintained at 25° C. Herein, the revolution of the rotary drum1108 was suspended.

Incidentally, as the rotary drum 1108 was rotated as above described,the substrate carrying mechanism 1110 was operated to take up thefollowing element substrate from the carriage belt 1115 and to unload itsuch that it was positioned on the following substrate holding segment1107, and the the element substrate was fastened so that it was securelyheld on the substrate holding segment, in the same manner as in the caseof the former element substrate (1102). Thereafter, on the carriage belt1115 from which the latter element substrate was taken up, the followingelement substrate was placed to stand by for the next treatment.

Now, when the element substrate (1120) was brought to the etchingtreatment zone and it was immersed in the electrolyte solution, thelifting mechanism 1105 having the counter electrode 1104 and a 1 mmthick silicone rubber gapping member (not shown) stacked in the namedorder on the surface thereof, was lifted to contact the gapping memberwith the transparent and electrically conductive film of the elementsubstrate (1102) held on the substrate holding segment 1107.

Herein, as the counter electrode 1104, there was used a patternedcounter electrode comprising a platinum plate with a 1 mm thick siliconerubber film bonded to cover the entire of a surface of said platinumplate and having a square groove of 30 cm×30 cm in size and 0.5 mm inwidth formed through the silicone rubber film such that the platinumplate is exposed in the square groove and the remaining rear and sidefaces of the platinum plate are insulated by an insulating film.

Then, the power source 1112 was switched on to apply a direct current of25 A between the counter electrode 1104 and the element substrate (1102)for 0.5 second while being controlled by the sequence controller 1114.

After this, the lifting mechanism 1105 was returned to home positiontogether with the gapping member and the counter electrode 1104.

Then, the rotary drum 1108 was again rotated to reach the zone forconducting the short circuit defects-eliminating treatment. Therevolution of the rotary drum 1108 was suspended. In this zone, thepower source 1113 was switched on to apply a D.C. bias voltage of 4.5 Vbetween the counter electrode 1106 and the element substrate (1102)while controlling by the sequence controller 1114. In this case, thecounter electrode 1106 was positioned in parallel to the elementsubstrate (1102) while maintaining an interval of 4.0 cm between thetwo.

Successively, the rotary drum 1108 was rotated, during which when theelement substrate (1102) held on the substrate holding segment 1107passed by the treated liquid removing mechanism 1111, air was sprayedagainst the element substrate (1102) by operating the treated liquidremoving mechanism to remove the electrolyte solution deposited on theelement substrate.

Thereafter, when the substrate holding segment 1107 (having the elementsubstrate (1102) free of the electrolyte solution held thereon) of therotary drum 1108 was returned to the starting position, the revolutionof the rotary drum 1108 was suspended, and the electromagnet was removedfrom the element substrate.

Successively, the substrate carrying mechanism 1110 was lowered to reachthe element substrate (1102) on the substrate holding segment 1107 ofthe rotary drum 1108 and to take up the element substrate (1102) fromthe rotary drum 1108. And the substrate carrying mechanism 1110 havingthe element substrate (1102) was horizontally moved to reach the othercarriage belt 1115 and to unload the element substrate (1102) on thecarriage belt. This carriage belt was operated to carry the elementsubstrate (1102) outside the apparatus. Thus, there was obtained aphotovoltaic element having a patterned transparent and electricallyconductive film and which is free of short circuit defects. The timerequired for the etching and defect-eliminating treatment was 10seconds.

The successive element substrates each held on the substrate holdingsegment 1107 of the rotary drum 1108 were continuously treated in thesame manner as in the case of the above element substrate (1102).

By this, the 100 photovoltaic elements obtained in the above step 1 werecontinuously treated to obtain 100 patterned photovoltaic elementshaving a patterned transparent and electrically conductive film andwhich is free of short circuit defects.

3. Preparation of solar cell:

Using the 100 patterned photovoltaic elements free of short circuitdefects obtained in the above step 2, solar cells were prepared inaccordance with the procedures described in the step 3 (preparation ofsolar cell) in Example 1.

EVALUATION

The resultant 100 solar cells were evaluated in the same manner as inExample 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1.

As a result, the mean value among the shunt resistances obtained for the100 solar cells was found to be 280 Ω.cm². All the solar cells werefound to be free of shunts.

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the manner as in Example 1.

As a result, all the solar cells were found to have a satisfactoryphotoelectric conversion efficiency in the range of 7.2±0.2%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result, the 100solar cells were found to be almost free of disconnection anddefectively etched portion and to have a uniformly etched line. Theyield was found to be 98%.

(3). Using some of the 100 solar cells and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For the resultant solar cell modules,reliability testing was conducted in the same manner as in Example 1. Asa result, the mean value among the deterioration proportions obtainedfor all the solar cell modules was found to be about 2.0% which issatisfactory.

From the evaluated results above described, the following facts areunderstood. That is, the patterning and the elimination of short circuitdefects can be surely conducted by the foregoing etching anddefect-eliminating treatment, and all the solar cells produced by way ofthe by the foregoing etching and defect-eliminating treatment are goodin initial characteristics and highly reliable. In addition, it isunderstood that the process according to the present invention enablesmass-production of a highly reliable solar cell without the necessity ofconducting any provisional step before and after the etching treatmentby way of electrolysis, and at an improved treatment speed and with ashort period of time required for the etching and defect-eliminatingtreatment.

EXAMPLE 6

In this example, there were prepared 100 p-i-n junction triple cell typeamorphous solar cells having the constitution shown in FIGS. 3(a) and3(b) while patterning their transparent and electrically conductivefilms and eliminating short circuit defects possibly created in thefabrication of said amorphous solar cell, using the apparatus shown inFIG. 10 capable of continuously conducting the etching process and theshort circuit defects-eliminating process, in the following manner.

1. Preparation of photovoltaic element:

In accordance with the procedures for the preparation of a photovoltaicelement, described in the step 1 (preparation of photovoltaic element)of Example 2, there were prepared 100 p-i-n junction triple cell typephotovoltaic elements.

2. Etching treatment and short circuit defects-eliminating treatment:

For the 100 photovoltaic elements obtained in the above step 1, etchingtreatment (patterning treatment) and short circuit defects-eliminatingtreatment (these treatments will be hereinafter referred to as etchingand defect-eliminating treatment) were continuously conducted in thesame manner as in the step 2 of Example 5.

Particularly, the 100 photovoltaic elements obtained in the above step 1were successively introduced into the apparatus shown in FIG. 10 andthey were continuously subjected to the etching treatment and shortcircuit defects-eliminating treatment in the same manner as in the step2 of Example 5, to thereby obtain 100 patterned photovoltaic elementshaving a patterned transparent and electrically conductive film andwhich is free of short circuit defects.

3. Preparation of solar cell:

Using the 100 patterned photovoltaic elements obtained in the above step2, 100 solar cells were prepared in accordance with the proceduresdescribed in the step 3 (preparation of solar cell) in Example 1.

EVALUATION

The resultant 100 solar cells were evaluated in the same manner as inExample 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1.

As a result, the mean value among the shunt resistances obtained for the100 solar cells was found to be 290 kΩ.cm². All the solar cells werefound to be free of shunts.

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the manner as in Example 1.

As a result, all the solar cells were found to have a satisfactoryphotoelectric conversion efficiency in the range of 9.2±0.2%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result , the 100solar cells were found to be almost free of disconnections anddefectively etched portions and to have a uniformly etched line. Theyield was found to be 98%.

(3). Using some of the 100 solar cells and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For the resultant solar cell modules,reliability testing was conducted in the same manner as in Example 1. Asa result, the mean value among the deterioration proportions obtainedfor all the solar cell modules was found to be about 2.1% which issatisfactory.

From the evaluated results above-described, the following facts areunderstood. That is, the patterning precision by the foregoing etchingtreatment is good, and all the solar cells produced by way of thepatterning by the foregoing etching treatment are good in initialcharacteristics and highly reliable. In addition, it is understood thatthe process according to the present invention enables mass-productionof a highly reliable solar cell without the necessity of conducting anyprovisional step before and after the etching treatment by way ofelectrolysis and at an improved treatment speed and with a short periodof time required for the etching treatment.

EXAMPLE 7

The procedures of Example 5 were repeated, except that instead of thedirect current of 25 A applied in the etching treatment, a pulse currentof 20 Å was applied five times between the counter electrode and theelement substrate, to thereby obtain 100 amorphous solar cells.

EVALUATION

The resultant 100 solar cells were evaluated in the same evaluationmanner as in Example 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1.

As a result, the mean value among the shunt resistances obtained for the100 solar cells was found to be 300 Ω.cm². And all the solar cells werefound to be free of a shunt created.

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the manner as in Example 1.

As a result, all the solar cells were found to have a satisfactoryphotoelectric conversion efficiency in the range of 7.1±0.2%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result, the 100solar cells were almost found to be free of disconnections anddefectively etched portions and to have a uniformly etched line. Theyield was found to be 98%.

(3). Using some of the 100 solar cells and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For the resultant solar cell modules,reliability testing was conducted in the same manner as in Example 1. Asa result, the mean value among the deterioration proportions obtainedfor all the solar cell modules was found to be about 2.1% which issatisfactory.

From the evaluated results above described, the following facts areunderstood. That is, the patterning precision by the foregoing etchingtreatment is good, and all the solar cells produced by way of thepatterning by the foregoing etching treatment are good in initialcharacteristics and highly reliable. In addition, it is understood thatthe process according to the present invention enables mass-productionof a highly reliable solar cell without the necessity of conducting anyprovisional steps before and after the etching treatment by way ofelectrolysis and at an improved treatment speed and with a short periodof time required for the etching treatment.

EXAMPLE 8

The procedures of Example 5 were repeated, except that instead of theD.C. bias voltage of 4.5 V applied in the etching treatment, a voltageof 4.5 was intermittently applied five times at a interval of 1 secondby way of pulse impression between the counter electrode and the elementsubstrate, to thereby obtain 100 amorphous solar cells.

EVALUATION

The resultant 100 solar cells were evaluated in the same evaluationmanner as in Example 1.

(1). For each solar cell, evaluation with respect to initialcharacteristics was conducted in the same manner as in Example 1.

As a result, the mean value among the shunt resistances obtained for the100 solar cells was found to be 410 kΩ.cm². All the solar cells werefound to be free of shunts.

(2). For each solar cell, evaluation with respect to photoelectricconversion efficiency was conducted in the manner as in Example 1.

As a result, all the solar cells were found to have a satisfactoryphotoelectric conversion efficiency in the range of 7.2±0.1%.

Successively, for each solar cell, the portions patterned by the etchingtreatment were examined by means of a microscope. As a result, the 100solar cells were almost found to be free of disconnections anddefectively etched portions and to have a uniformly etched line. Theyield was found to be 98%.

(3). Using some of the 100 solar cells and in accordance with aconventional process for producing a solar cell module by way of theconventional thermocompression lamination treatment, there were obtaineda plurality of solar cell modules. For the resultant solar cell modules,reliability testing was conducted in the same manner as in Example 1. Asa result, the mean value among the deterioration proportions obtainedfor all the solar cell modules was found to be about 2.0% which issatisfactory.

From the results above-described, the following facts are understood.That is, the patterning precision by the foregoing etching treatment isgood, and all the solar cells produced by way of the patterning by theforegoing etching treatment are good in initial characteristics andhighly reliable. In addition, it is understood that the processaccording to the present invention enables mass-production of a highlyreliable solar cell without the necessity of conducting any provisionalstep before and after the etching treatment by way of electrolysis andat an improved treatment speed and with a short period of time requiredfor the etching treatment.

What is claimed is:
 1. A method for etching a substrate having a portionto be etched, comprising the steps of:(a) immersing said substrate in anelectrolyte solution such that said substrate serves as a negativeelectrode, (b) arranging a counter electrode having a patterncorresponding to a desired etching pattern to be formed at said portionto be etched of said substrate in said electrolyte solution so as tomaintain an interval between said counter electrode and said substrate,and (c) applying a direct current or a pulse current between saidsubstrate and said counter electrode to etch said portion to be etchedof said substrate into a pattern corresponding to said pattern of saidcounter electrode.
 2. The method according to claim 1, wherein thesubstrate is positioned in close proximity to the counter electrode. 3.The method according to claim 1, wherein the interval between thesubstrate and the counter electrode is in the range of from 0.1 mm to 2mm.
 4. The method according to claim 1, wherein the portion to be etchedof the substrate comprises a film formed on the substrate.
 5. The methodaccording to claim 4, wherein the film is a transparent and electricallyconductive film.
 6. The method according to claim 4, wherein the filmcomprises at least a material formed by means of vacuum evaporation,ionization evaporation, sputtering, CVD, plasma CVD, or spraying.
 7. Themethod according to claim 1, wherein the portion to be etched of thesubstrate comprises a film formed on the substrate through asemiconductor layer.
 8. The method according to claim 7, wherein thefilm is a transparent and electrically conductive film.
 9. The methodaccording to claim 1, wherein the portion to be etched of the substratecomprises a transparent and electrically conductive film.
 10. The methodaccording to claim 1, wherein a gapping member is positioned between thesubstrate and the counter electrode.
 11. The method according to claim10, wherein the gapping member comprises a soft material.
 12. The methodaccording claim 10, wherein the gapping member comprises a siliconerubber or a silicone sponge.
 13. The method according claim 1, whereinthe portion to be etched of the substrate comprises at least a materialselected from the group consisting of SnO₂, In₂ O₃, and ITO (indiumtinoxide).
 14. The method according to claim 1, wherein the electrolytesolution contains at least a compound selected from the group consistingof sodium chloride, potassium chloride, aluminum chloride, zincchloride, tin chloride, ferric chloride, sodium nitride, potassiumnitride, hydrochloric acid, nitric acid, and sulfuric acid as anelectrolyte.
 15. The method according to claim 1, wherein the counterelectrode comprises at least a material selected from the groupconsisting of platinum, carbon, gold, stainless steel, nickel, copperand lead.
 16. The method according to claim 1, wherein etching theportion to be etched of the substrate is conducted while contacting anon-etching portion of the portion to be etched with a gapping memberarranged on the counter electrode side.
 17. A process for producing asemiconductor device, comprising the steps of:(a) a step of immersing asubstrate for a semiconductor device and having a portion comprising afilm to be etched in an electrolyte solution such that said substrateserves as a negative electrode, (b) a step of arranging a counterelectrode having a pattern corresponding to a desired etching pattern tobe formed at said portion to be etched of said substrate in saidelectrolyte solution so as to maintain an interval between said counterelectrode and said substrate, and (c) an etching step of applying adirect current or a pulse current between said substrate and saidcounter electrode to etch said portion to be etched of said substrateinto a pattern corresponding to said pattern of said counter electrode.18. The process according to claim 17, wherein the substrate ispositioned in close proximity to the counter electrode.
 19. The processaccording to claim 17, wherein the interval between the substrate andthe counter electrode is in the range of from 0.1 mm to 2 mm.
 20. Theprocess according to claim 17, wherein the portion to be etchedcomprises a film formed on the substrate.
 21. The process according toclaim 20, wherein the film is a transparent and electrically conductivefilm.
 22. The process according to claim 20, wherein the film comprisesat least a material formed by means of vacuum evaporation, ionizationevaporation, sputtering, CVD, plasma CVD, or spraying.
 23. The processaccording to claim 17, wherein the portion to be etched comprises a filmformed on the substrate through a semiconductor layer.
 24. The processaccording to claim 23, wherein the film is a transparent andelectrically conductive film.
 25. The process according to claim 23,wherein the semiconductor layer has at least a combination of an n-typelayer, an i-type layer and a p-type layer.
 26. The process according toclaim 23, wherein the semiconductor layer contains a material selectedfrom the group consisting of an amorphous material, polycrystallinematerial, microcrystalline material and single-crystalline material. 27.The process according to claim 17, wherein the portion to be etchedcomprises a transparent and electrically conductive film.
 28. Theprocess according to claim 17, wherein a gapping member is positionedbetween the substrate and the counter electrode.
 29. The processaccording to claim 28, wherein the gapping member comprises a softmaterial.
 30. The process according claim 28, wherein the gapping membercomprises a silicone rubber or a silicone sponge.
 31. The processaccording claim 17, wherein the portion to be etched comprises at leasta material selected from the group consisting of SnO₂, In₂ O₃, and ITO(indiumtin oxide).
 32. The process according to claim 17, wherein theelectrolyte solution contains at least a compound selected from thegroup consisting of sodium chloride, potassium chloride, aluminumchloride, zinc chloride, tin chloride, ferric chloride, sodium nitride,potassium nitride, hydrochloric acid, nitric acid, and sulfuric acid asan electrolyte.
 33. The process according to claim 17, wherein thecounter electrode comprises at least a material selected from the groupconsisting of platinum, carbon, gold, stainless steel, nickel, copperand lead.
 34. The process according to claim 17, wherein etching theportion to be etched is conducted while contacting a non-etching portionof the portion to be etched with a gapping member arranged on thecounter electrode side.
 35. The process according to claim 17 whichfurther comprises conducting a defect elimination step after the etchingstep (c), said defect elimination step comprising subjecting the etchedproduct obtained in the etching step (c) to electrolytic reduction byapplying a direct current or a pulse current to cause a forward bias onthe substrate side whereby removing at least a non-etched film presentaround a defective portion of the etched portion of the etched product.36. The process according to claim 35, wherein the etching step (c) andthe defect elimination step are conducted in the same electrolytesolution.
 37. The process according to claim 35, wherein the distancebetween the portion to be etched and the counter electrode in the defectelimination step is made to be greater than that between the portion tobe etched and the counter electrode in the etching step (c).
 38. Theprocess according to claim 35, wherein the defect elimination step isconducted using an electrolyte solution containing at least a compoundselected from the group consisting of sodium chloride, potassiumchloride, aluminum chloride, zinc chloride, tin chloride, ferricchloride, sodium nitride, potassium nitride, hydrochloric acid, nitricacid, and sulfuric acid as an electrolyte.
 39. The process according toclaim 17, wherein the semiconductor device is a photosemiconductordevice.
 40. The process according to claim 17, wherein the semiconductordevice is a photovoltaic element.